The change-up comes as McDonald's Corp. fights to step up its image, as sales have slumped amid changing tastes and intensifying competition

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McDonald's is partnering with Chobani to offer Greek yogurt parfaits and smoothies at its Southern California restaurants as the fast-food giant works to transform into a "modern, progressive burger company."

McDonald's spokeswoman Lisa McComb said the partnership is limited to a regional test of about 800 restaurants in Los Angeles and San Diego.

"It's very premature to determine if it may expand," she wrote.

The Southern California restaurants are offering a "Simple Delights Menu" that lists options like apple slices, smoothies and the yogurt parfait made with Chobani.

SoCal restaurants also began selling two breakfast bowls this week. One is made with egg whites, turkey sausage, spinach and kale. The other is made with scrambled eggs and chorizo and includes a hash brown. The chain had tested the bowls on a more limited basis last year, which McComb said was for "operational learnings and customer feedback."

The change-up comes as McDonald's Corp. fights to step up its image, as sales have slumped amid changing tastes and intensifying competition. CEO Steve Easterbrook, who took over last March, has said he wants to transform McDonald's into a "modern, progressive burger company." One of the biggest moves under Easterbrook was the introduction of an all-day breakfast menu in October, which generated positive headlines for the company.

Whether it leads to sustained sales growth remains to be seen. In January, McDonald's said sales jumped 5.7 percent at established U.S. locations in the last three months of 2015, marking its best showing in four years. But the company did not disclose how much of the increase was driven by an uptick in customer visits, versus factors such as price hikes.